International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Paper: Improved security analysis of OMAC

Authors:
Mridul Nandi
Download:
URL: http://eprint.iacr.org/2007/292
Search ePrint
Search Google
Abstract: We present an improved security analysis of OMAC, the construction is widely used as a candidate of MAC or Pseudo Random Function (or PRF). In this direction, the first result was given in Crypto-05 where an improved security analysis of CBC (for fixed length or for arbitrary length prefix-free messages) had provided. Followed by this work, improved bounds for XCBC, TMAC and PMAC were found. The improved bounds are of the form $\mathrm{O}(\frac{Lq^2}{2^n})$ where the original bounds are $\mathrm{O}(\frac{\sigma^2}{2^n})$ which is roughly $\mathrm{O}(\frac{L^2q^2}{2^n})$. Here, a distinguisher can make at most $q$ queries having at most $\sigma$ many blocks with $L$ as the maximum block size. The original bound for OMAC was roughly $\frac{5L^2q^2}{2^n}$ shown in FSE-03 and the next improved bound was $\frac{4\sigma^2}{2^n}$ shown in Indocrypt-03. In this paper we have provided an improved bound (a similar form as provided for others) for OMAC and the bound we show is roughly $\frac{4q\sigma}{2^n} = \mathrm{O}(\frac{Lq^2}{2^n})$.
BibTeX
@misc{eprint-2007-13572,
  title={Improved security analysis of OMAC},
  booktitle={IACR Eprint archive},
  keywords={secret-key cryptography /},
  url={http://eprint.iacr.org/2007/292},
  note={ mridul.nandi@gmail.com 13723 received 29 Jul 2007},
  author={Mridul Nandi},
  year=2007
}